1. A word used to acknowledge the presence of a fellow companion
2. For a man to express interest in a particularly impressive female specimen
3. To contact via telephone

1. Is that mah boy ova there? HOLLAAAAA!
2. Watch out, I'm bout to holla at this fine bitch.
3. Boy, it was absolutely magnificent to see you again. Holla at me this evening, we can have tea and crumpets.